In modern semiconductor chip (“chip”) design, standard cells are placed on the chip to define a particular logic function. To ensure that each standard cell will be manufacturable when arbitrarily placed on the chip, each standard cell is defined to have an edge exclusion zone sized equal to one-half of a design rule (DR) spacing requirement between adjacent conductive features. In this manner, when any two standard cells are placed next to each other, their combined exclusion zone sizes at their interfacing boundaries will equal at least the DR spacing requirement between adjacent conductive features. Thus, the exclusion zone enables features to be placed arbitrarily within a standard cell without concern for cell-to-cell interface problems. However, when many standard cells are placed together on the chip, the edge exclusion zones associated with the standard cells can combine to occupy an expensive amount of chip area.
In view of the foregoing, it is of interest to optimize cell layout and placement such that chip area and routing resources can be most efficiently utilized, particularly when cells are defined according to a constrained layout architecture.